function check_input(){
            form = document.getElementById("input_info");
            user_inputs = form.getElementsByTagName("input");
            for (var i=0; i<user_inputs.length; i++){
                if (user_inputs[i].value == ''){
                    alert("输入不能为空，请将所有信息填写完整。");
                    return -1;
                }
            }

            //Submit if check pass
            sub = document.getElementById("submit");
            sub.type = "submit";

        }